Patients with all types of chronic blepharitis are being evaluated from a clinical and laboratory standpoint. This is leading to the development of a classification system that is more appropriate to the presentation of these diseases in the post antibiotic and steroid era. The evaluations include a complete bacteriological evaluation of all patients. This portion of the project is aimed at determining whether or not bacteria play a primary or secondary role in the expression of the various disease processes. Meibomian secretions are also being evaluated biochemically to determine the composition of these secretions in normal individuals and in patients with chronic blepharitis. It is possible that an alteration in meibomian secretions may contribute to the development of the disease process in patients with meibomitis. Frequently isolated bacteria are being evaluated for the production of lipolytic exoenzymes, i.e. cholesterol esterase, fatty wax esterase, and triglyceride lipase. Staphylococcus epidermidis is also being evaluated for the production of a cholesterol esterifying enzyme. The potential inhibitory effect of tetracycline on these various enzymes will be evaluated. The melting and spreading temperatures of meibomian secretions and controls in patients is being evaluated as is tear pH. It is planned to assess the lid temperature in patients and controls. An attempt is being made to determine if Demodex has an association with any of the types of chronic blepharitis. A new facet is that tears will be evaluated for protein, immunoglobulin, and prostaglandin composition in normal controls and in all groups of patients with chronic blepharitis. Double-masked, randomized, clinical therapeutic trials will be undertaken to determine the usefulness of topical antibiotics or oral tetracycline.